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174955
Tue, 04/12/2011 - 17:22
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https://oananews.org//node/174955
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Japan ups Fukushima nuke crisis severity to 7, same as Chernobyl
TOKYO (Kyodo) - Japan raised the severity level of the ongoing emergency at the crippled Fukushima Daiichi nuclear plant on Tuesday from level 5 to the maximum 7 on an international scale, recognizing that the tsunami-caused accident matches the world's worst nuclear catastrophe in 1986 at Chernobyl.
The government's Nuclear and Industrial Safety Agency upgraded its provisional evaluation based on an estimate that radioactive materials far exceeding the criteria for level 7 have so far been released into the external environment, but added the release from the Fukushima plant is about 10 percent of that from the former Soviet nuclear plant.
The nuclear regulatory agency under the industry ministry and the Nuclear Safety Commission of Japan, a government panel, said that between 370,000 and 630,000 terabecquerels of radioactive materials have been emitted into the air from the Nos. 1 to 3 reactors of the plant.
Level 7 accidents on the International Nuclear Event Scale correspond to the release into the external environment of radioactive materials equal to more than tens of thousands of terabecquerels of radioactive iodine 131. One terabecquerel equals 1 trillion becquerels.
Chief Cabinet Secretary Yukio Edano said the government is ''sorry to Fukushima residents, the Japanese people and the international community'' over the nuclear disaster caused by the massive March 11 quake and tsunami.
The plant operator Tokyo Electric Power Co. also offered an apology to the public for being still unable to stop the radiation leakage, pointing to the possibility that the total emission of radioactive substances could eventually surpass that of the Chernobyl incident.
A considerable amount of the radioactive materials emitted is believed to originate from the plant's No. 2 reactor, whose containment vessel's pressure suppression chamber was damaged by an explosion on March 15, said Kenkichi Hirose, a Cabinet Office adviser serving for the safety commission, at a news conference.
''Our estimates suggest the amount of radioactive materials released into the air sharply rose on March 15 and 16 after abnormalities were detected at the No. 2 reactor,'' Hirose said. ''The cumulative amount of leaked radiation has been gradually on the rise, but we believe the current emission level is significantly low.''
The safety commission said it estimates the release has come down to under 1 terabecquerel per hour.
Japan believes the Fukushima crisis is different from the Chernobyl accident in many ways, said Hidehiko Nishiyama, a spokesman for the nuclear agency.
As examples, Nishiyama said no one in Fukushima has died from acute diseases caused by exposure to massive amount of radiation, compared with about 30 in the accident that happened in the former Soviet Union, and that the reactors themselves did not explode as in Chernobyl.
''Even though some amount of radiation keeps leaking from reactors and their containment vessels, they are not totally destroyed and are functioning,'' Nishiyama said.
Hirose ruled out the possibility that the evacuation zone set by the government within 20 kilometers from the plant will be reviewed following the upgrading of the severity level.
Nishiyama said it took about a month to raise the severity level of the Fukushima contingency due to a delay in securing reliable monitoring data. On March 18, the agency had provisionally set the level at 5, the same as the Three Mile Island accident in the United States in 1979.
The provisional judgment will be finalized after examinations by a government panel of nuclear experts, Nishiyama said, adding the government will further bolster radiation monitoring to collect data.
The INES only reflects radiation emitted into the air, and Japan needs to independently assess the severity of the incident by also monitoring contamination levels in the sea and soil, he said.
Earlier, the safety commission released a preliminary calculation for the cumulative amount of radiation, saying it has exceeded the yearly limit of 1 millisievert in areas extending more than 60 km northwest of the plant and about 40 km south-southwest of the plant.
Within the 20-km exclusion zone, the amount varied from under 1 millisievert to 100 millisieverts or more, and in the 20-30 km ring where residents are asked to stay indoors it came to nearly 50 millisieverts.
The government's Nuclear and Industrial Safety Agency upgraded its provisional evaluation based on an estimate that radioactive materials far exceeding the criteria for level 7 have so far been released into the external environment, but added the release from the Fukushima plant is about 10 percent of that from the former Soviet nuclear plant.
The nuclear regulatory agency under the industry ministry and the Nuclear Safety Commission of Japan, a government panel, said that between 370,000 and 630,000 terabecquerels of radioactive materials have been emitted into the air from the Nos. 1 to 3 reactors of the plant.
Level 7 accidents on the International Nuclear Event Scale correspond to the release into the external environment of radioactive materials equal to more than tens of thousands of terabecquerels of radioactive iodine 131. One terabecquerel equals 1 trillion becquerels.
Chief Cabinet Secretary Yukio Edano said the government is ''sorry to Fukushima residents, the Japanese people and the international community'' over the nuclear disaster caused by the massive March 11 quake and tsunami.
The plant operator Tokyo Electric Power Co. also offered an apology to the public for being still unable to stop the radiation leakage, pointing to the possibility that the total emission of radioactive substances could eventually surpass that of the Chernobyl incident.
A considerable amount of the radioactive materials emitted is believed to originate from the plant's No. 2 reactor, whose containment vessel's pressure suppression chamber was damaged by an explosion on March 15, said Kenkichi Hirose, a Cabinet Office adviser serving for the safety commission, at a news conference.
''Our estimates suggest the amount of radioactive materials released into the air sharply rose on March 15 and 16 after abnormalities were detected at the No. 2 reactor,'' Hirose said. ''The cumulative amount of leaked radiation has been gradually on the rise, but we believe the current emission level is significantly low.''
The safety commission said it estimates the release has come down to under 1 terabecquerel per hour.
Japan believes the Fukushima crisis is different from the Chernobyl accident in many ways, said Hidehiko Nishiyama, a spokesman for the nuclear agency.
As examples, Nishiyama said no one in Fukushima has died from acute diseases caused by exposure to massive amount of radiation, compared with about 30 in the accident that happened in the former Soviet Union, and that the reactors themselves did not explode as in Chernobyl.
''Even though some amount of radiation keeps leaking from reactors and their containment vessels, they are not totally destroyed and are functioning,'' Nishiyama said.
Hirose ruled out the possibility that the evacuation zone set by the government within 20 kilometers from the plant will be reviewed following the upgrading of the severity level.
Nishiyama said it took about a month to raise the severity level of the Fukushima contingency due to a delay in securing reliable monitoring data. On March 18, the agency had provisionally set the level at 5, the same as the Three Mile Island accident in the United States in 1979.
The provisional judgment will be finalized after examinations by a government panel of nuclear experts, Nishiyama said, adding the government will further bolster radiation monitoring to collect data.
The INES only reflects radiation emitted into the air, and Japan needs to independently assess the severity of the incident by also monitoring contamination levels in the sea and soil, he said.
Earlier, the safety commission released a preliminary calculation for the cumulative amount of radiation, saying it has exceeded the yearly limit of 1 millisievert in areas extending more than 60 km northwest of the plant and about 40 km south-southwest of the plant.
Within the 20-km exclusion zone, the amount varied from under 1 millisievert to 100 millisieverts or more, and in the 20-30 km ring where residents are asked to stay indoors it came to nearly 50 millisieverts.
